int (*write)(naContext c, void* f, char* buf, unsigned int len);
void (*seek) (naContext c, void* f, unsigned int off, int whence);
int (*tell) (naContext c, void* f);
int (*write)(naContext c, void* f, char* buf, unsigned int len);
void (*seek) (naContext c, void* f, unsigned int off, int whence);
int (*tell) (naContext c, void* f);